I have the unfortunate combination of being very sensitive to bed bugs (bites while sleeping wake me in about 30 seconds, sometimes quickly enough to catch the bug red-jawed, then consistently swell about 2-3cm in diameter...) and travelling a lot recently in parts of Africa and London that have bed bug problems. On the plus side, it means I can answer this question...
I've found most forms of insect repellent including DEET-based ones to be somewhat helpful, but not enough to rely on them alone. Whereas mozzies might be deterred from flying near you, hungry bed bugs will find a way to reach that spot you missed unless you take other precautions. That spot might well be inside your clothes...
Turns out there's proper evidence to back up my experience that bedbugs don't like DEET:
Repellency of selected chemicals against the bed bug (Hemiptera: Cimicidae)
...[DEET] provided a high level of repellency against bed bugs... At 25% concentration, DEET-treated fabric surface remained highly repellent to bed bugs for a 14-d period...
...Isolongifolenone and isolongifolanone, two natural products and recently reported insect repellents, exhibited strong repellent property against bed bugs but at significantly lower levels than DEET. Three novel potential repellent compounds discovered by Bedoukian Research Inc. (Danbury, CT) exhibited similar level of repellency and longevity as DEET for repelling bed bugs...
Here's what's saved me when I've discovered the hard way that my bed for the night is infested at 2am:
- Bed bugs dislike light, so having a light is a good short-term deterrent. Don't rely on it too much though - the more bugs there are, and the more times you do this, the less of a deterrent it'll be (in some chronically infested places I've even seen bedbugs cheerfully strolling along white walls in daylight - that's rare though). Ideally, there'll be something like a desk lamp: get rid of any blankets etc, point it at the bed, and try to sleep curled up in the middle so they'd have to go further through the light to reach you. It'll help for one or two nights, unless the bugs are famished.
- A circle of insect repellent on the bedsheets around you also helps. Be careful if using DEET because it can melt some synthetic fabrics, test on a small corner first. This isn't just to stop them biting, it's to discourage them from getting somewhere they can stow away until any repellent you're wearing wears off, or, worse, until you get back home...
- If you need a pillow, check one very thoroughly for bugs, especially folds, seams and inside corners, then use only that one. Get others off the bed to give them less cover. Keep the pillow you use away from the headboard or edge of the bed within the circle of light and insect repellent - if you're alone, sleeping diagonally helps.
- Cover up as best you can. The best option is an insect-repellent-treated sleeping bag liner (few places sell them but you can buy fabric treating insect repellent (example) in many outdoors shops - be aware that some of the repellents used for these have "exhibited low levels of repellency against bed bugs" - deterring around ~30%, similar to 2.5% DEET whereas 5% DEET deterred 100% in the same test. Better than nothing, not a substitute for DEET, but a handy extra line of defence. Pyjamas or similar light clothes tucked in at the waist and tucked in to socks also gives them less options. Tuck sleeves into gloves if possible. Use insect repellent on hands, head, shoulders and feet (feet because they can usually bite through socks - the socks are to stop the buggers strolling along up inside your bedclothes...)
Doing all of the above gave me an uninterrupted 6 hours sleep with no bites (after the initial 2am jolt) in a very badly infested place recently.
Also make sure you don't take them home with you:
- Keep clothes, luggage etc as far away from the bed somewhere in the room you seldom go (i.e. less CO2 from your breath to entice curious bugs), ideally away from bedbug-friendly surfaces. Bathroom is ideal if there is one.
- Consider some insect repellent on or around your luggage if it won't damage it or the furnishings (again, be careful with DEET)
- Seal and close everything that can be sealed and closed, don't make it easy for them
- Wash thoroughly!
- Change clothes before going anywhere near your next bed. Wash them if you can, seal them in a tied bag if you can't, and check accessories like belts
- After arriving at your next destination, keep everything as far from your bed as possible, wash what you can from your luggage, and check corners and seams in your luggage for stealthy stowaways.
If you've got access to something like a balcony or shed or similar, for an extra precaution, consider putting luggage and fabric items you had with you in "quarantine" out there for a few days, with the nearest doors and windows to your home sealed so they don't have any easy human-scented route in.
Regarding itch suppression, I'm a bit of an extreme case... so results may differ. For me, regular bite creams like anti-histamines don't seem to help much (no reason not to try them though, just don't rely on them). I've had best results with:
- Rubbing nearly dry soap (or, if regular bars of soap aren't available, a blob of undiluted hand soap) on the bite and leaving it. Don't know why this works, but it helps a little.
- Those bite "clickers" that give the bite a very small static electric shock. Again, no idea why they work, but they help a little